Nonaqueous electrolyte compositions comprising lithium glycolatoborate and fluorinated solvent

ABSTRACT

Disclosed herein are electrolyte compositions comprising: a non-fluorinated carbonate; a fluorinated solvent; a lithium glycolatoborate compound represented by Formula I or Formula II: 
     
       
         
         
             
             
         
       
     
     a fluorinated carbonate; and an electrolyte salt. The electrolyte compositions are useful in electrochemical cells, such as lithium batteries.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Nos.62/092,916 filed on Dec. 17, 2014, and 62/197,771 filed on Jul. 28,2015, which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The disclosure herein relates to electrolyte compositions containing afluorinated solvent and a lithium glycolatoborate, which are useful inelectrochemical cells, such as lithium ion batteries.

BACKGROUND

With the advancement in portable electronic devices and intense interestin plug-in hybrid electric vehicles, there is great demand to increasethe energy and power capabilities of lithium ion batteries. In thisregard, increasing the operational voltage is a viable strategy. Currentlithium ion battery electrolyte solvents typically contain one or morelinear carbonates, such as ethyl methyl carbonate, dimethyl carbonate,or diethyl carbonate; and a carbonate, such as ethylene carbonate.However, at cathode potentials above 4.2 V these electrolyte candecompose, which can result in a loss of battery performance. What isneeded is a formulation that combines solvent(s) with additive(s) thatwill have improved cycling performance at high temperature when used ina lithium ion battery, particularly such a battery that operates with ahigh potential cathode.

SUMMARY

Disclosed herein are electrolyte compositions comprising:

-   -   a) a non-fluorinated carbonate;    -   b) a fluorinated solvent;    -   c) at least one of a lithium glycolatoborate compound        represented by Formula I or Formula II:

-   -   d) a fluorinated carbonate; and    -   e) an electrolyte salt.        The non-fluorinated carbonate may be cyclic or acyclic. The        fluorinated solvent may be a fluorinated acyclic carboxylic acid        ester, a fluorinated acyclic carbonate, a fluorinated acyclic        ether, or mixtures thereof. In one embodiment, the fluorinated        carbonate is a cyclic fluorinated carbonate.

In one embodiment there is a provided a method to prepare an electrolytecomposition, the method comprising combining: a) the non-fluorinatedcarbonate; b) the fluorinated solvent; c) at least one of a lithiumglycolato borate compound; d) the fluorinated carbonate; and e) theelectrolyte salt, as defined herein, to form an electrolyte composition.

In another embodiment, there is provided herein an electrochemical cellcomprising an electrolyte composition disclosed herein. In a furtherembodiment, the electrochemical cell is a lithium ion battery.

DETAILED DESCRIPTION

As used above and throughout the disclosure, the following terms, unlessotherwise indicated, shall be defined as follows:

The term “electrolyte composition” as used herein, refers to a chemicalcomposition suitable for use as an electrolyte in an electrochemicalcell.

The term “electrolyte salt” as used herein, refers to an ionic salt thatis at least partially soluble in the solvent of the electrolytecomposition and that at least partially dissociates into ions in thesolvent of the electrolyte composition to form a conductive electrolytecomposition.

The term “anode” refers to the electrode of an electrochemical cell, atwhich oxidation occurs. In a galvanic cell, such as a battery, the anodeis the negatively charged electrode. In a secondary (i.e. rechargeable)battery, the anode is the electrode at which oxidation occurs duringdischarge and reduction occurs during charging.

The term “cathode” refers to the electrode of an electrochemical cell,at which reduction occurs. In a galvanic cell, such as a battery, thecathode is the positively charged electrode. In a secondary (i.e.rechargeable) battery, the cathode is the electrode at which reductionoccurs during discharge and oxidation occurs during charging.

The term “lithium ion battery” refers to a type of rechargeable batteryin which lithium ions move from the anode to the cathode duringdischarge and from the cathode to the anode during charge.

Equilibrium potential between lithium and lithium ion is the potentialof a reference electrode using lithium metal in contact with thenon-aqueous electrolyte containing lithium salt at a concentrationsufficient to give about 1 mole/liter of lithium ion concentration, andsubjected to sufficiently small currents so that the potential of thereference electrode is not significantly altered from its equilibriumvalue (Li/Li⁺). The potential of such a Li/Li⁺ reference electrode isassigned here the value of 0.0V. Potential of an anode or cathode meansthe potential difference between the anode or cathode and that of aLi/Li⁺ reference electrode. Herein voltage means the voltage differencebetween the cathode and the anode of a cell, neither electrode of whichmay be operating at a potential of 0.0V.

The term “carbonate” as used herein refers specifically to an organiccarbonate, wherein the organic carbonate is a dialkyl diester derivativeof carbonic acid, the organic carbonate having a general formulaR′OCOOR″, wherein R′ and R″ are each independently selected from alkylgroups having at least 1 carbon atom, wherein the alkyl substituents canbe the same or different, can be saturated or unsaturated, substitutedor unsubstituted, can form a cyclic structure via interconnected atoms,or include a cyclic structure as a substituent of either or both of thealkyl groups.

The term “alkyl group”, as used herein, refers to a linear or branchedchain hydrocarbon group containing no unsaturation.

The term “fluoroalkyl group”, as used herein, refers to an alkyl groupwherein at least one hydrogen is replaced by fluorine.

Disclosed herein are electrolyte compositions comprising:

-   -   a) a non-fluorinated carbonate;    -   b) a fluorinated solvent;    -   c) at least one of a lithium glycolatoborate compound        represented by Formula I or Formula II:

-   -   d) a fluorinated carbonate; and    -   e) an electrolyte salt.

As used herein, the terms “fluorinated carbonate” and “fluorinatedsolvent” refer to different compounds, that is, not the same chemicalcompound.

One or more non-fluorinated carbonates may be used in the electrolytecomposition. The non-fluorinated carbonate may be cyclic or acyclic.Suitable non-fluorinated carbonates include ethylene carbonate, ethylmethyl carbonate, dimethyl carbonate, diethyl carbonate, vinylenecarbonate, di-tert-butyl carbonate, vinylethylene carbonate,dimethylvinylene carbonate, propylene carbonate, ethyl propyl vinylenecarbonate, dimethylvinylene carbonate, or mixtures thereof. In oneembodiment the non-fluorinated carbonate comprises ethylene carbonate,propylene carbonate, or mixtures thereof. In one embodiment, thenon-fluorinated carbonate comprises ethylene carbonate. In oneembodiment, the non-fluorinated carbonate comprises propylene carbonate.In one embodiment, the non-fluorinated carbonate comprises ethyl methylcarbonate. In one embodiment, the non-fluorinated carbonate comprisesdimethyl carbonate.

In another embodiment the non-fluorinated cyclic carbonate comprises amixture of ethylene carbonate and vinylene carbonate, where the vinylenecarbonate makes up 0.2 to 3% of the weight of the formulatedelectrolyte.

In the electrolyte compositions disclosed herein, the non-fluorinatedcarbonate or mixtures thereof can be used in various amounts dependingon the desired properties of the electrolyte composition. In oneembodiment, the non-fluorinated carbonate(s) in combination is presentin the electrolyte composition in the range of about 0.5 percent toabout 95 percent by weight of the electrolyte composition, or about 5percent to about 95 percent, or about 10 percent to about 80 percent,about 20 percent to about 40 percent, or about 25 percent to about 35percent by weight of the electrolyte composition. In another embodiment,the non-fluorinated carbonate is present in the range of about 0.5percent to about 10 percent by weight, or about 1 percent to about 10percent, or about 5 percent to about 10 percent by weight of theelectrolyte composition.

The fluorinated solvent may be a fluorinated acyclic carboxylic acidester, a fluorinated acyclic carbonate, a fluorinated acyclic ether, ormixtures thereof. One or more fluorinated solvents may be used in theelectrolyte composition. In one embodiment, the fluorinated solvent is afluorinated acyclic carboxylic acid ester. In one embodiment, thefluorinated solvent is a fluorinated acyclic carbonate. In oneembodiment, the fluorinated solvent is a fluorinated acyclic ether.

Suitable fluorinated acyclic carboxylic acid esters are represented bythe formula

R¹—COO—R²

wherein

-   -   i) R¹ is H, an alkyl group, or a fluoroalkyl group;    -   ii) R² is an alkyl group or a fluoroalkyl group;    -   iii) either or both of R¹ and R² comprises fluorine; and    -   iv) R¹ and R², taken as a pair, comprise at least two carbon        atoms but not more than seven carbon atoms.

In one embodiment, R¹ is H and R² is a fluoroalkyl group. In oneembodiment, R¹ is an alkyl group and R² is a fluoroalkyl group. In oneembodiment, R¹ is a fluoroalkyl group and R² is an alkyl group. In oneembodiment, R¹ is a fluoroalkyl group and R² is a fluoroalkyl group, andR¹ and R² can be either the same as or different from each other. In oneembodiment, R¹ comprises one carbon atom. In one embodiment, R¹comprises two carbon atoms.

In another embodiment, R¹ and R² are as defined herein above, and R¹ andR², taken as a pair, comprise at least two carbon atoms but not morethan seven carbon atoms and further comprise at least two fluorineatoms, with the proviso that neither R¹ nor R² contains a FCH₂— group ora —FCH— group.

In one embodiment, the number of carbon atoms in R¹ in the formula aboveis 1, 3, 4, or 5.

Examples of suitable fluorinated acyclic carboxylic acid esters includewithout limitation CH₃—COO—CH₂CF₂H (2,2-difluoroethyl acetate, CAS No.1550-44-3), CH₃—COO—CH₂CF₃ (2,2,2-trifluoroethyl acetate, CAS No.406-95-1), CH₃CH₂—COO—CH₂CF₂H (2,2-difluoroethyl propionate, CAS No.1133129-90-4), CH₃—COO—CH₂CH₂CF₂H (3,3-difluoropropyl acetate),CH₃CH₂—COO—CH₂CH₂CF₂H (3,3-difluoropropyl propionate),HCF₂—CH₂—CH₂—COO—CH₂CH₃ (ethyl 4,4-difluorobutanoate, CAS No.1240725-43-2), CH₃—COO—CH₂CF₃ (2,2,2-trifluoroethyl acetate, CAS No.406-95-1), H—COO—CH₂CF₂H (difluoroethyl formate, CAS No. 1137875-58-1),H—COO—CH₂CF₃ (trifluoroethyl formate, CAS No. 32042-38-9), and mixturesthereof. In one embodiment, the fluorinated acyclic carboxylic acidester comprises 2,2-difluoroethyl acetate (CH₃—COO—CH₂CF₂H). In oneembodiment, the fluorinated acyclic carboxylic acid ester comprises2,2-difluoroethyl propionate (CH₃CH₂—COO—CH₂CF₂H). In one embodiment,the fluorinated acyclic carboxylic acid ester comprises2,2,2-trifluoroethyl acetate (CH₃—COO—CH₂CF₃). In one embodiment, thefluorinated acyclic carboxylic acid ester comprises 2,2-difluoroethylformate (H—COO—CH₂C F₂H).

Suitable fluorinated acyclic carbonates are represented by the formula:

R³—OCOO—R⁴

wherein

-   -   i) R³ is a fluoroalkyl group;    -   ii) R⁴ is an alkyl group or a fluoroalkyl group; and    -   iii) R³ and R⁴ taken as a pair comprise at least two carbon        atoms but not more than seven carbon atoms.

In one embodiment, R³ is a fluoroalkyl group and R⁴ is an alkyl group.In one embodiment, R³ is a fluoroalkyl group and R⁴ is a fluoroalkylgroup, and R³ and R⁴ can be either the same as or different from eachother. In one embodiment, R³ and R⁴ independently can be branched orlinear. In one embodiment, R³ comprises one carbon atom. In oneembodiment, R³ comprises two carbon atoms.

In another embodiment, R³ and R⁴ are as defined herein above, and R³ andR⁴, taken as a pair, comprise at least two carbon atoms but not morethan seven carbon atoms and further comprise at least two fluorineatoms, with the proviso that neither R³ nor R⁴ contains a FCH₂— group ora —FCH— group.

Examples of suitable fluorinated acyclic carbonates include withoutlimitation CH₃—OC(O)O—CH₂CF₂H (methyl 2,2-difluoroethyl carbonate, CASNo. 916678-13-2), CH₃—OC(O)O—CH₂CF₃ (methyl 2,2,2-trifluoroethylcarbonate, CAS No. 156783-95-8), CH₃—OC(O)O—CH₂CF₂CF₂H (methyl2,2,3,3-tetrafluoropropyl carbonate, CAS No. 156783-98-1),HCF₂CH₂—OCOO—CH₂CH₃ (2,2-difluoroethyl ethyl carbonate, CAS No.916678-14-3), and CF₃CH₂—OCOO—CH₂CH₃ (2,2,2-trifluoroethyl ethylcarbonate, CAS No. 156783-96-9).

Suitable fluorinated acyclic ethers are represented by the formula:

R⁵—O—R⁶

wherein

-   -   i) R⁵ is a fluoroalkyl group;    -   ii) R⁶ is an alkyl group or a fluoroalkyl group; and    -   iii) R⁵ and R⁶ taken as a pair comprise at least two carbon        atoms but not more than seven carbon atoms.

In one embodiment, R⁵ is a fluoroalkyl group and R⁶ is an alkyl group.In one embodiment, R⁵ is a fluoroalkyl group and R⁶ is a fluoroalkylgroup, and R⁵ and R⁶ can be either the same as or different from eachother. In one embodiment, R⁵ and R⁶ independently can be branched orlinear. In one embodiment, R⁵ comprises one carbon atom. In oneembodiment, R⁵ comprises two carbon atoms.

In another embodiment, R⁵ and R⁶ are as defined herein above, and R⁵ andR⁶, taken as a pair, comprise at least two carbon atoms but not morethan seven carbon atoms and further comprise at least two fluorineatoms, with the proviso that neither R⁵ nor R⁶ contains a FCH₂— group ora —FCH— group.

Examples of suitable fluorinated acyclic ethers include withoutlimitation HCF₂CF₂CH₂—O—CF₂CF₂H (CAS No. 16627-68-2) andHCF₂CH₂—O—CF₂CF₂H (CAS No. 50807-77-7).

A mixture of two or more of these fluorinated acyclic carboxylic acidester, fluorinated acyclic carbonate, and/or fluorinated acyclic ethersolvents may also be used. As used herein, the term “mixtures”encompasses both mixtures within and mixtures between solvent classes,for example mixtures of two or more fluorinated acyclic carboxylic acidesters, and also mixtures of fluorinated acyclic carboxylic acid estersand fluorinated acyclic carbonates, for example. Non-limiting examplesinclude a mixture of 2,2-difluoroethyl acetate and 2,2-difluoroethylpropionate, or a mixture of 2,2-difluoroethyl acetate and 2,2difluoroethyl methyl carbonate.

In one embodiment, the fluorinated solvent is:

-   -   a) a fluorinated acyclic carboxylic acid ester represented by        the formula:

R¹—COO—R²,

-   -   b) a fluorinated acyclic carbonate represented by the formula:

R³—OCOO—R⁴,

-   -   c) a fluorinated acyclic ether represented by the formula:

R⁵—O—R⁶,

-   -   or mixtures thereof;        wherein    -   i) R¹ is H, an alkyl group, or a fluoroalkyl group;    -   ii) R³ and R⁵ is each independently a fluoroalkyl group and can        be either the same as or different from each other;    -   iii) R², R⁴, and R⁶ is each independently an alkyl group or a        fluoroalkyl group and can be either the same as or different        from each other;    -   iv) either or both of R¹ and R² comprises fluorine; and    -   v) R¹ and R², R³ and R⁴, and R⁵ and R⁶, each taken as a pair,        comprise at least two carbon atoms but not more than seven        carbon atoms.

In another embodiment, the fluorinated solvent is

-   -   a) a fluorinated acyclic carboxylic acid ester represented by        the formula:

R¹—COO—R²,

-   -   b) a fluorinated acyclic carbonate represented by the formula:

R³—OCOO—R⁴,

-   -   c) a fluorinated acyclic ether represented by the formula:

R⁵—O—R⁶,

-   -   or mixtures thereof;        wherein    -   i) R¹ is H, an alkyl group, or a fluoroalkyl group;    -   ii) R³ and R⁵ is each independently a fluoroalkyl group and can        be either the same as or different from each other;    -   iii) R², R⁴, and R⁶ is each independently an alkyl group or a        fluoroalkyl group and can be either the same as or different        from each other;    -   iv) either or both of R¹ and R² comprises fluorine; and    -   v) R¹ and R², R³ and R⁴, and R⁵ and R⁶, each taken as a pair,        comprise at least two carbon atoms but not more than seven        carbon atoms and further comprise at least two fluorine atoms,        with the proviso that none of R¹, R², R³, R⁴, R⁵, nor R⁶        contains a FCH₂— group or a —FCH— group.

In the electrolyte compositions disclosed herein, the fluorinatedsolvent or mixtures thereof can be used in various amounts depending onthe desired properties of the electrolyte composition. In someembodiments, the electrolyte composition comprises from about 5 weightpercent to about 95 weight percent of the fluorinated solvent. In someembodiments, the electrolyte composition comprises from about 10 weightpercent to about 90 weight percent, or from about 10 weight percent toabout 80 weight percent, or from about 20 weight percent to about 80weight percent, or from about 30 weight percent to about 80 weightpercent, or from about 40 weight percent to about 80 weight percent, orfrom about 50 weight percent to about 80 weight percent, or from about60 weight percent to about 80 weight percent fluorinated solvent. Insome embodiments, the fluorinated solvent is present in the electrolytecomposition in a percentage by weight that is defined by a lower limitand an upper limit. The lower limit of the range is 5, 10, 20, 25, 30,35, 40, 45, 50, 55, 60, or 65 and the upper limit of the range is 70,75, 80, 85, 90, 95, 96, 97, 98, or 99. All percentages by weight arebased on the total weight of the electrolyte composition.

Fluorinated acyclic carboxylic acid esters, fluorinated acycliccarbonates, and fluorinated acyclic ethers suitable for use herein maybe prepared using known methods. For example, acetyl chloride may bereacted with 2,2-difluoroethanol (with or without a basic catalyst) toform 2,2-difluoroethyl acetate. Additionally, 2,2-difluoroethyl acetateand 2,2-difluoroethyl propionate may be prepared using the methoddescribed by Wiesenhofer et al. (WO 2009/040367 A1, Example 5).Alternatively, 2,2-difluoroethyl acetate can be prepared using themethod described in the Examples herein below. Other fluorinated acycliccarboxylic acid esters may be prepared using the same method usingdifferent starting carboxylate salts. Similarly, methyl chloroformatemay be reacted with 2,2-difluoroethanol to form methyl 2,2-difluoroethylcarbonate. Synthesis of HCF₂CF₂CH₂—O—CF₂CF₂H can be done by reacting2,2,3,3-tetrafluoropropanol with tetrafluoroethylene in the presence ofbase (e.g., NaH, etc.). Similarly, reaction of 2,2-difluoroethanol withtetrafluoroethylene yields HCF₂CH₂—O—CF₂CF₂H. Alternatively, some ofthese fluorinated solvents may be obtained commercially. For bestresults, it is desirable to purify the fluorinated acyclic carboxylicesters and fluorinated acyclic carbonates to a purity level of at leastabout 99.9%, for example at least about 99.99%. These fluorinatedsolvents may be purified using distillation methods such as vacuumdistillation or spinning band distillation.

The electrolyte compositions disclosed herein also comprise afluorinated carbonate that is different than the fluorinated solvent. Inone embodiment, the fluorinated carbonate is a cyclic fluorinatedcarbonate. In one embodiment, suitable cyclic fluorinated carbonates canbe represented by the following structure

wherein

-   -   i) each of A, B, C, and D is H, F, a saturated or unsaturated C₁        to C₄ alkyl group, or a saturated or unsaturated C₁ to C₄        fluoroalkyl group, and can be the same as or different from each        other; and    -   ii) at least one of A, B, C, and D comprises fluorine.        The term “unsaturated”, as used herein, refers to an        olefinically unsaturated group containing at least one        carbon-carbon double bond.

Suitable cyclic fluorinated carbonates include 4-fluoroethylenecarbonate (abbreviated as FEC, also known as4-fluoro-1,3-dioxolan-2-one), difluoroethylene carbonate isomers,trifluoroethylene carbonate isomers, tetrafluoroethylene carbonate,2,2,3,3-tetrafluoropropyl methyl carbonate,bis(2,2,3,3-tetrafluoropropyl) carbonate, bis(2,2,2-trifluoroethyl)carbonate, 2,2,2-trifluoroethyl methyl carbonate, bis(2,2-difluoroethyl)carbonate, 2,2-difluoroethyl methyl carbonate, methyl2,3,3-trifluoroallyl carbonate, or mixtures thereof. In one embodimentthe fluorinated carbonate comprises fluoroethylene carbonate. In oneembodiment, the fluorinated carbonate comprises4-fluoro-1,3-dioxolan-2-one; 4,5-difluoro-1,3-dioxolan-2-one;4,5-difluoro-4-methyl-1,3-dioxolan-2-one;4,5-difluoro-4,5-dimethyl-1,3-dioxolan-2-one;4,4-difluoro-1,3-dioxolan-2-one; 4,4,5-trifluoro-1,3-dioxolan-2-one; ormixtures thereof.

In one embodiment, the electrolyte composition comprises about 0.01weight percent to about 10 weight percent, or about 0.1 weight percentto about 5 weight percent, or about 0.5 weight percent to about 3 weightpercent, or about 1 weight percent to about 3 weight percent or about1.5 weight percent to about 2.5 weight percent, or about 2 weightpercent, fluorinated carbonate, based on the total weight of theelectrolyte composition.

The electrolyte compositions disclosed herein also comprise at least oneof a lithium glycolatoborate compound represented by Formula I orFormula II:

In one embodiment, the lithium glycolatoborate compound is lithiumbis(glycolato) borate, which is shown in Formula I. In anotherembodiment, the lithium glycolatoborate compound is lithiumdifluoro(glycolato) borate, which is shown in Formula II. In anotherembodiment, the lithium glycolatoborate compound comprises a mixture oflithium bis(glycolato) borate and lithium difluoro(glycolato) borate.

In one embodiment, at least one lithium glycolatoborate is present atabout 0.01 weight percent to about 10 weight percent, or about 0.1weight percent to about 5 weight percent, or about 0.5 weight percent toabout 3 weight percent, or about 0.5 weight percent to about 2 weightpercent or about 0.5 weight percent to about 1.5 weight percent, orabout 1 weight percent, of the total electrolyte composition.

Other lithium borate salts may additionally be present, such as but notlimited to lithium bis(oxalato)borate, lithium difluoro(oxalato)borate,lithium tetrafluoroborate, and mixtures thereof.

In one embodiment the electrolyte composition comprises about 0.5 weightpercent to about 5 weight percent of a cyclic fluorinated carbonate andabout 0.01 weight percent to about 5 weight percent of at least one of alithium glycolatoborate compound of Formula I or Formula II, based onthe weight of the electrolyte composition.

In some embodiments, the electrolyte composition comprises ethylenecarbonate, 2,2-difluoroethyl acetate, lithium bis(glycolato) borate, andfluoroethylene carbonate. In some embodiments, the electrolytecomposition comprises ethylene carbonate, 2,2-difluoroethyl acetate,lithium difluoro(glycolato) borate, and fluoroethylene carbonate. Insome embodiments, the electrolyte composition comprises propylenecarbonate, 2,2-difluoroethyl acetate, lithium bis(glycolato) borate, andfluoroethylene carbonate. In some embodiments, the electrolytecomposition comprises propylene carbonate, 2,2-difluoroethyl acetate,lithium difluoro(glycolato) borate, and fluoroethylene carbonate. Insome embodiments, the electrolyte composition comprises ethyl methylcarbonate, 2,2-difluoroethyl acetate, lithium bis(glycolato) borate, andfluoroethylene carbonate. In some embodiments, the electrolytecomposition comprises ethyl methyl carbonate, 2,2-difluoroethyl acetate,lithium difluoro(glycolato) borate, and fluoroethylene carbonate. Insome embodiments, the electrolyte composition comprises dimethylcarbonate, 2,2-difluoroethyl acetate, lithium bis(glycolato) borate, andfluoroethylene carbonate. In some embodiments, the electrolytecomposition comprises dimethyl carbonate, 2,2-difluoroethyl acetate,lithium difluoro(glycolato) borate, and fluoroethylene carbonate.

The electrolyte compositions disclosed herein also contain at least oneelectrolyte salt. Suitable electrolyte salts include without limitation

lithium hexafluorophosphate (LiPF₆),

lithium bis(trifluromethyl)tetrafluorophosphate (LiPF₄(CF₃)₂),

lithium bis(pentafluoroethyl)tetrafluorophosphate (LiPF₄(C₂F₅)₂),

lithium tris(pentafluoroethyl)trifluorophosphate (LiPF₃(C₂F₅)₃),

lithium bis(trifluoromethanesulfonyl)imide,

lithium bis(perfluoroethanesulfonyl)imide,

lithium (fluorosulfonyl) (nonafluorobutanesulfonyl)imide,

lithium bis(fluorosulfonyl)imide,

lithium tetrafluoroborate,

lithium perchlorate,

lithium hexafluoroarsenate,

lithium trifluoromethanesulfonate,

lithium tris(trifluoromethanesulfonyl)methide,

lithium bis(oxalato)borate,

lithium difluoro(oxalato)borate,

Li₂B₁₂F_(12-x)H_(x) where x is equal to 0 to 8, and

mixtures of lithium fluoride and anion receptors such as B(OC₆F₅)₃.

Mixtures of two or more of these or comparable electrolyte salts mayalso be used. In one embodiment, the electrolyte salt is lithiumhexafluorophosphate. The electrolyte salt can be present in theelectrolyte composition in an amount of about 0.2 to about 2.0 M, moreparticularly about 0.3 to about 1.5 M, and more particularly about 0.5to about 1.2 M.

Electrolyte compositions disclosed herein can additionally or optionallycomprise additives that are known to those of ordinary skill in the artto be useful in conventional electrolyte compositions, particularly foruse in lithium ion batteries. For example, electrolyte compositionsdisclosed herein can also include gas-reduction additives which areuseful for reducing the amount of gas generated during charging anddischarging of lithium ion batteries. Gas-reduction additives can beused in any effective amount, but can be included at an amount in therange of from about 0.05 weight percent to about 10 weight percent,alternatively from about 0.05 weight percent to about 5 weight percentof the electrolyte composition, or alternatively from about 0.5 weightpercent to about 2 weight percent of the electrolyte composition.

Suitable gas-reduction additives that are known conventionally include,for example: halobenzenes such as fluorobenzene, chlorobenzene,bromobenzene, iodobenzene, or haloalkylbenzenes; succinic anhydride;ethynyl sulfonyl benzene; 2-sulfobenzoic acid cyclic anhydride; divinylsulfone; triphenylphosphate (TPP); diphenyl monobutyl phosphate (DMP);γ-butyrolactone; 2,3-dichloro-1,4-naphthoquinone; 1,2-naphthoquinone;2,3-dibromo-1,4-naphthoquinone; 3-bromo-I,2-naphthoquinone;2-acetylfuran; 2-acetyl-5-methylfuran; 2-methylimidazole1-(phenylsulfonyl)pyrrole; 2,3-benzofuran;fluoro-cyclotriphosphazenes such as2,4,6-trifluoro-2-phenoxy-4,6-dipropoxy-cyclotriphosphazene and2,4,6-trifluoro-2-(3-(trifluoromethyl)phenoxy)-6-ethoxy-cyclotriphosphazene;benzotriazole; perfluoroethylene carbonate; anisole; diethylphosphonate;fluoroalkyl-substituted dioxolanes such as 2-trifluoromethyldioxolaneand 2,2-bistrifluoromethyl-1,3-dioxolane; trimethylene borate;dihydro-3-hydroxy-4,5,5-trimethyl-2(3H)-furanone;dihydro-2-methoxy-5,5-dimethyl-3(2H)-furanone;dihydro-5,5-dimethyl-2,3-furandione; propene sultone; diglycolic acidanhydride; di-2-propynyl oxalate; 4-hydroxy-3-pentenoic acid γ-lactone;CF₃COOCH₂C(CH₃)(CH₂OCOCF₃)₂; CF₃COOCH₂CF₂CF₂CF₂CF₂CH₂OCOCF₃;α-methylene-γ-butyrolactone; 3-methyl-2(5H)-furanone;5,6-dihydro-2-pyranone; diethylene glycol, diacetate; triethylene glycoldimethacrylate; triglycol diacetate; 1,2-ethanedisulfonic anhydride;1,3-propanedisulfonic anhydride; 2,2,7,7-tetraoxide 1,2,7-oxadithiepane;3-methyl-2,2,5,5-tetraoxide 1,2,5-oxadithiolane;hexamethoxycyclotriphosphazene;4,5-dimethyl-4,5-difluoro-1,3-dioxolan-2-one;2-ethoxy-2,4,4,6,6-pentafluoro-2,2,4,4,6,6-hexahydro-1,3,5,2,4,6-triazatriphosphorine;2,2,4,4,6-pentafluoro-2,2,4,4,6,6-hexahydro-6-methoxy-1,3,5,2,4,6-triazatriphosphorine;4,5-difluoro-1,3-dioxolan-2-one; 1,4-bis(ethenylsulfonyl)-butane;bis(vinylsulfonyl)-methane; 1,3-bis(ethenylsulfonyl)-propane;1,2-bis(ethenylsulfonyl)-ethane; and1,1′-[oxybis(methylenesulfonyl)]bis-ethene.

Other suitable additives that can be used are HF scavengers, such assilanes, silazanes (Si—NH—Si), epoxides, amines, aziridines (containingtwo carbons), salts of carbonic acid such as lithium oxalate, B₂O₅, ZnOor other metal oxide, and fluorinated inorganic salts.

In another embodiment, there is provided herein an electrochemical cellcomprising a housing, an anode and a cathode disposed in the housing andin ionically conductive contact with one another, an electrolytecomposition, as described above, providing an ionically conductivepathway between the anode and the cathode, and a porous or microporousseparator between the anode and the cathode. The housing may be anysuitable container to house the electrochemical cell components. Theanode and the cathode may be comprised of any suitable conductingmaterial depending on the type of electrochemical cell. Suitableexamples of anode materials include without limitation lithium metal,lithium metal alloys, lithium titanate, aluminum, platinum, palladium,graphite, transition metal oxides, and lithiated tin oxide. Suitableexamples of cathode materials include without limitation graphite,aluminum, platinum, palladium, electroactive transition metal oxidescomprising lithium or sodium, indium tin oxide, and conducting polymerssuch as polypyrrole and polyvinylferrocene.

The porous separator serves to prevent short circuiting between theanode and the cathode. The porous separator typically consists of asingle-ply or multi-ply sheet of a microporous polymer such aspolyethylene, polypropylene, or a combination thereof. The pore size ofthe porous separator is sufficiently large to permit transport of ions,but small enough to prevent contact of the anode and cathode eitherdirectly or from particle penetration or dendrites which can from on theanode and cathode.

In another embodiment, the electrochemical cell is a lithium ionbattery. Suitable cathode materials for a lithium ion battery includewithout limitation electroactive compounds comprising lithium andtransition metals, such as LiCoO₂, LiNiO₂, LiMn₂O₄, LiCO_(0.2)Ni_(0.2)O₂or LiV₃O₈;

Li_(a)CoG_(b)O₂ (0.90≦a≦1.8, and 0.001≦b≦0.1);

Li_(a)Ni_(b)Mn_(c)Co_(d)R_(e)O_(2−f)Z_(f) where 0.8≦a≦1.2, 0.1≦b≦0.9,0.0≦c≦0.7, 0.05≦d≦0.4, 0≦e≦0.2, wherein the sum of b+c+d+e is about 1,and 00.08;

Li_(a)A_(1−b),R_(b)D₂ (0.90≦a≦1.8 and 0≦b≦0.5);

Li_(a)E_(1−b)R_(b)O_(2−c)D_(c) (0.90≦a≦1.8, 0≦b≦0.5 and 0≦c≦0.05);

Li_(a)Ni_(1−b−c)Co_(b)R_(c)O_(2−d)Z_(d) where 0.9≦a≦1.8, 0≦b≦0.4,0≦c≦0.05, and 0≦d≦0.05;

Li_(1+z)Ni_(1−x−y)Co_(x)Al_(y)O₂ where 0<x<0.3, 0<y<0.1, and 0<z<0.06;

LiNi_(0.5)Mn_(1.5)O₄; LiFePO₄, LiMnPO₄, LiCoPO₄, and LiVPO₄F.

In one embodiment, the electroactive compound includesLi_(a)Ni_(b)Mn_(c)Co_(d)R_(e)O_(2−f)Z_(f) as defined above with theexceptions that 0.1 b 0.5 and also 0.2≦c≦0.7.

In the above chemical formulas A is Ni, Co, Mn, or a combinationthereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or acombination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or acombination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, Zr, Ti, arare earth element, or a combination thereof; Z is F, S, P, or acombination thereof. Suitable cathodes and cathode active materialsinclude those disclosed in U.S. Pat. Nos. 5,962,166; 6,680,145;6,964,828; 7,026,070; 7,078,128; 7,303,840; 7,381,496; 7,468,223;7,541,114; 7,718,319; 7,981,544; 8,389,160; 8,394,534; and 8,535,832,and the references therein. By “rare earth element” is meant thelanthanide elements from La to Lu, and Y and Sc. In another embodimentthe cathode material is an NMC cathode; that is, a LiNiMnCoO cathode.More specifically, cathodes in which the atomic ratio of Ni:Mn:Co is1:1:1 (Li_(a)Ni_(1−b−c)Co_(b)R_(c)O_(2−d)Z_(d) where 0.98≦a≦1.05,0≦d≦0.05, b=0.333, c=0.333, where R comprises Mn) or where the atomicratio of Ni:Mn:Co is 5:3:2 (Li_(a)Ni_(1−b−c)Co_(b)R_(c)O_(2−d)Z_(d)where 0.98≦a≦1.05, 0≦d≦0.05, c=0.3, b=0.2, where R comprises Mn). Inanother embodiment, the cathode in the lithium ion battery disclosedherein comprises a composite material of the formulaLi_(a)Mn_(b)J_(c)O₄Z_(d), wherein J is Ni, Co, Mn, Cr, Fe, Cu, V, Ti,Zr, Mo, B, Al, Ga, Si, Li, Mg, Ca, Sr, Zn, Sn, a rare earth element, ora combination thereof; Z is F, S, P, or a combination thereof; and0.9≦a≦1.2, 1.3≦b≦2.2, 0≦c≦0.7, 0≦d≦0.4.

In another embodiment, the cathode in the lithium ion battery disclosedherein comprises a cathode active material exhibiting greater than 30mAh/g capacity in the potential range greater than 4.6 V versus a Li/Li⁺reference electrode. One example of such a cathode is a stabilizedmanganese cathode comprising a lithium-containing manganese compositeoxide having a spinel structure as cathode active material. Thelithium-containing manganese composite oxide in a cathode suitable foruse herein comprises oxides of the formulaLi_(x)Ni_(y)M_(z)Mn_(2−y−z)O_(4−d), wherein x is 0.03 to 1.0; x changesin accordance with release and uptake of lithium ions and electronsduring charge and discharge; y is 0.3 to 0.6; M comprises one or more ofCr, Fe, Co, Li, Al, Ga, Nb, Mo, Ti, Zr, Mg, Zn, V, and Cu; z is 0.01 to0.18; and d is 0 to 0.3. In one embodiment in the above formula, y is0.38 to 0.48, z is 0.03 to 0.12, and d is 0 to 0.1. In one embodiment inthe above formula, M is one or more of Li, Cr, Fe, Co and Ga. Stabilizedmanganese cathodes may also comprise spinel-layered composites whichcontain a manganese-containing spinel component and a lithium richlayered structure, as described in U.S. Pat. No. 7,303,840.

In another embodiment, the cathode in the lithium ion battery disclosedherein comprises a composite material represented by the structure offormula:

x(Li_(2−w)A_(1−v)Q_(w+v)O_(3−e)).(1−x)(Li_(y)Mn_(2−z)M_(z)O_(4−d))

wherein:

x is about 0.005 to about 0.1;

A comprises one or more of Mn or Ti;

Q comprises one or more of Al, Ca, Co, Cr, Cu, Fe, Ga, Mg, Nb, Ni, Ti,V, Zn, Zr or Y;

e is 0 to about 0.3;

v is 0 to about 0.5.

w is 0 to about 0.6;

M comprises one or more of Al, Ca, Co, Cr, Cu, Fe, Ga, Li, Mg, Mn, Nb,Ni, Si, Ti, V, Zn, Zr or Y;

d is 0 to about 0.5;

y is about 0 to about 1; and

z is about 0.3 to about 1; and

wherein the Li_(y)Mn_(2−z)M_(z)O_(4−d) component has a spinel structureand the Li_(2−w)Q_(w+v)A_(1−v)O_(3−e) component has a layered structure.

Alternatively, in another embodiment, in the Formula

x(Li_(2−w)A_(1−v)Q_(w+v)O_(3−e)).(1−x)(Li_(y)Mn_(2−z)M_(z)O_(4−d))

x is about 0 to about 0.1, and all ranges for the other variables are asstated above.

In another embodiment, the cathode in the lithium ion battery disclosedherein comprises:

Li_(a)A_(1−x)R_(x)DO_(4−f)Z_(f),

wherein:

A is Fe, Mn, Ni, Co, V, or a combination thereof;

R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, Zr, Ti, a rare earth element, ora combination thereof;

D is P, S, Si, or a combination thereof;

Z is F, Cl, S, or a combination thereof;

0.8≦a≦2.2;

0≦x≦0.3; and

0≦f≦0.1.

In another embodiment, the cathode in the lithium ion battery disclosedherein comprises a cathode active material which is charged to apotential greater than or equal to about 4.1 V, or greater than 4.35 V,or greater than 4.5 V, or greater than 4.6 V versus a Li/Li⁺ referenceelectrode. Other examples are layered-layered high-capacityoxygen-release cathodes such as those described in U.S. Pat. No.7,468,223 charged to upper charging potentials above 4.5 V.

Particles of the above cathode compositions may be coated with one ormore of polymer, carbon, metal oxide, metal fluoride, or metalphosphate. Suitable coatings include, MgO, CaO, SrO, CeO₂, La₂O₃, TiO₂,Fe₂O₃, ZrO₂, MoO₃, MoO₂, ZnO, SiO₂, SnO₂, B₂O₃, Li₂O.2B₂O₃, Al₂O₃,LiAlO₂, Ga₂O₃, MnSiO₄, Li₄P₂O₇, Li₃PO₄, AlPO₄, Mg₃(PO₄)₂, CoPO₄,Zn₃(PO₄)₂BiOF, AlF₃, or combinations thereof. Other suitable coatingmaterials include those compositions in the above list of cathodecompositions.

A cathode active material suitable for use herein can be prepared usingmethods such as the hydroxide precursor method described by Liu et al(J. Phys. Chem. C 13:15073-15079, 2009). In that method, hydroxideprecursors are precipitated from a solution containing the requiredamounts of manganese, nickel and other desired metal(s) acetates by theaddition of KOH. The resulting precipitate is oven-dried and then firedwith the required amount of LiOH.H₂O at about 800 to about 1000° C. inoxygen for 3 to 24 hours. Alternatively, the cathode active material canbe prepared using a solid phase reaction process or a sol-gel process asdescribed in U.S. Pat. No. 5,738,957 (Amine).

A cathode, in which the cathode active material is contained, suitablefor use herein may be prepared by methods such as mixing an effectiveamount of the cathode active material (e.g. about 70 wt % to about 97 wt%), a polymer binder, such as polyvinylidene difluoride, and conductivecarbon in a suitable solvent, such as N-methylpyrrolidone, to generate apaste, which is then coated onto a current collector such as aluminumfoil, and dried to form the cathode.

A lithium ion battery as disclosed herein further contains an anode,which comprises an anode active material that is capable of storing andreleasing lithium ions. Examples of suitable anode active materialsinclude without limitation silicon, lithium metal, lithium alloys suchas lithium-aluminum alloy, lithium-lead alloy, lithium-silicon alloy,lithium-tin alloy and the like; carbon materials such as graphite andmesocarbon microbeads (MCMB); phosphorus-containing materials such asblack phosphorus, MnP₄ and CoP₃, metal oxides such as SnO₂, SnO andTiO₂, nanocomposites containing antimony or tin, for examplenanocomposites containing antimony, oxides of aluminum, titanium, ormolybdenum, and carbon, such as those described by Yoon et al (Chem.Mater. 21, 3898-3904, 2009); and lithium titanates such as Li₄Ti₅O₁₂ andLiTi₂O₄. In one embodiment, the anode active material is lithiumtitanate, graphite, lithium alloys, silicon, and combinations thereof.In another embodiment, the anode is graphite. In one embodiment, theanode comprises an anode active material and the anode active materialis lithium titanate or graphite.

An anode can be made by a method similar to that described above for acathode wherein, for example, a binder such as a vinylidenefluoride-based copolymer, styrene-butadiene copolymer, or carboxymethylcellulose is dissolved or dispersed in an organic solvent or water,which is then mixed with the active, conductive material to obtain apaste. The paste is coated onto a metal foil, preferably aluminum orcopper foil, to be used as the current collector. The paste is dried,preferably with heat, so that the active mass is bonded to the currentcollector. Suitable anode active materials and anodes are availablecommercially from companies such as Hitachi Chemical (Ibaraki, Japan),NEI Inc. (Somerset, N.J.), and Farasis Energy Inc. (Hayward, Calif.).

A lithium ion battery as disclosed herein also contains a porousseparator between the anode and cathode. The porous separator serves toprevent short circuiting between the anode and the cathode. The porousseparator typically consists of a single-ply or multi-ply sheet of amicroporous polymer such as polyethylene, polypropylene, polyamide orpolyimide, or a combination thereof. The pore size of the porousseparator is sufficiently large to permit transport of ions to provideionically conductive contact between the anode and cathode, but smallenough to prevent contact of the anode and cathode either directly orfrom particle penetration or dendrites which can from on the anode andcathode. Examples of porous separators suitable for use herein aredisclosed in U.S. Patent Application Publication No. 2012/0149852, nowU.S. Pat. No. 8,518,525.

The housing of the lithium ion battery hereof may be any suitablecontainer to house the lithium ion battery components described above.Such a container may be fabricated in the shape of small or largecylinder, a prismatic case or a pouch.

The electrolyte compositions disclosed herein are useful in many typesof electrochemical cells and batteries such as capacitors, nonaqueousbatteries such as lithium batteries, flow batteries, and fuel cells.

The electrochemical cells and lithium ion battery disclosed herein maybe used for grid storage or as a power source in variouselectronically-powered or -assisted devices (“electronic device”) suchas a computer, a camera, a radio or a power tool, varioustelecommunications devices, or various transportation devices (includinga motor vehicle, automobile, truck, bus or airplane).

In another embodiment there is a provided a method to prepare anelectrolyte composition. The method comprises combining:

-   -   a) the non-fluorinated carbonate;    -   b) the fluorinated solvent;    -   c) at least one of a lithium glycolatoborate compound        represented by Formula I or Formula II;    -   d) the fluorinated carbonate; and    -   e) the electrolyte salt, as defined herein, to form an        electrolyte composition. The step of combining can be        accomplished by adding the individual components of the        electrolyte composition sequentially or at the same time. The        components can be combined in any suitable order. In some        embodiments, the components a), b), c) and d) are combined to        make a first solution. After the formation of the first        solution, an amount of the electrolyte salt is added to the        first solution to produce the electrolyte composition having the        desired concentration of the electrolyte salt. Typically, the        electrolyte composition is stirred during and/or after the        addition of the components in order to form a homogeneous        mixture.

EXAMPLES

The meaning of abbreviations used is as follows: “g” means gram(s), “mg”means milligram(s), “pg” means microgram(s), “L” means liter(s), “mL”means milliliter(s), “mol” means mole(s), “mmol” means millimole(s), “M”means molar concentration, “wt %” means percent by weight, “mm” meansmillimeter(s), “ppm” means parts per million, “h” means hour(s), “min”means minute(s), “A” means amperes, “mA” mean milliampere(s), “mAh/g”mean milliamperes hour(s) per gram, “V” means volt(s), “xC” refers to aconstant current which is the product of x and a current in A which isnumerically equal to the nominal capacity of the battery expressed inAh, “Pa” means pascal(s), “rpm” means revolutions per minute, “NMR”means nuclear magnetic resonance spectroscopy, “GC/MS” means gaschromatography/mass spectrometry.

Materials and Methods Representative Preparation of 2,2-DifluoroethylAcetate

The 2,2-difluoroethyl acetate (DFEA) used in the following Examples wasprepared by reacting potassium acetate with HCF₂CH₂Br. The following isa typical procedure used for the preparation.

Potassium acetate (Aldrich, Milwaukee, Wis., 99%) was dried at 100° C.under a vacuum of 0.5-1 mm of Hg (66.7-133 Pa) for 4 to 5 h. The driedmaterial had a water content of less than 5 ppm, as determined by KarlFischer titration. In a dry box, 212 g (2.16 mol, 8 mol % excess) of thedried potassium acetate was placed into a 1.0-L, 3 neck round bottomflask containing a heavy magnetic stir bar. The flask was removed fromthe dry box, transferred into a fume hood, and equipped with athermocouple well, a dry ice condenser, and an additional funnel.

Sulfolane (500 mL, Aldrich, 99%, 600 ppm of water as determined by KarlFischer titration) was melted and added to the 3 neck round bottom flaskas a liquid under a flow of nitrogen. Agitation was started and thetemperature of the reaction medium was brought to about 100° C.HCF₂CH₂Br (290 g, 2 mol, E.I. du Pont de Nemours and Co., 99%) wasplaced in the addition funnel and was slowly added to the reactionmedium. The addition was mildly exothermic and the temperature of thereaction medium rose to 120-130° C. in 15-20 min after the start of theaddition. The addition of HCF₂CH₂Br was kept at a rate which maintainedthe internal temperature at 125-135° C. The addition took about 2-3 h.The reaction medium was agitated at 120-130° C. for an additional 6 h(typically the conversion of bromide at this point was about 90-95%).Then, the reaction medium was cooled down to room temperature and wasagitated overnight. Next morning, heating was resumed for another 8 h.

At this point the starting bromide was not detectable by NMR and thecrude reaction medium contained 0.2-0.5% of 1,1-difluoroethanol. Thedry-ice condenser on the reaction flask was replaced by a hose adapterwith a Teflon® valve and the flask was connected to a mechanical vacuumpump through a cold trap (−78° C., dry-ice/acetone). The reactionproduct was transferred into the cold trap at 40-50° C. under a vacuumof 1-2 mm Hg (133 to 266 Pa). The transfer took about 4-5 h and resultedin 220-240 g of crude HCF₂CH₂OC(O)CH₃ of about 98-98.5% purity, whichwas contaminated by a small amount of HCF₂CH₂Br (about 0.1-0.2%),HCF₂CH₂OH (0.2-0.8%), sulfolane (about 0.3-0.5%) and water (600-800ppm). Further purification of the crude product was carried out usingspinning band distillation at atmospheric pressure. The fraction havinga boiling point between 106.5-106.7° C. was collected and the impurityprofile was monitored using GC/MS (capillary column HP5MS, phenyl-methylsiloxane, Agilent 19091S-433, 30 m, 250 μm, 0.25 μm; carrier gas —He,flow rate 1 mL/min; temperature program: 40° C., 4 min, temp. ramp 30°C./min, 230° C., 20 min). Typically, the distillation of 240 g of crudeproduct gave about 120 g of HCF₂CH₂OC(O)CH₃ of 99.89% purity, (250-300ppm H₂O) and 80 g of material of 99.91% purity (containing about 280 ppmof water). Water was removed from the distilled product by treatmentwith 3 A molecular sieves, until water was not detectable by KarlFischer titration (i.e., <1 ppm).

Synthesis of Lithium Tetramethanolatoboron

Glassware was dried overnight at 120° C. in an oven. The glassware wasthen brought into a nitrogen filled dry box. In the multineck flasklithium methoxide (37.97 g, 0.1057 mol) and 50 mL anhydrous methanolwere combined with a stir bar. The flask was sealed with a septum andbrought out of the dry box. Under nitrogen a reflux condenser was added.The reaction was heated to 60° C. with an oil bath until the solutionshould become homogenous. Dropwise over 5 minutes trimethyl borate (12.4mL, 0.1110 mol) was added via syringe through the septum. The reactionwas stirred overnight then allowed to cool to room temperature. Themethanol was removed via syringe and the solid was dried under highvacuum at 35° C. The flask was sealed and brought into a dry box where11.5 g product was collected.

Synthesis of Lithium Bis(Glycolato) Borate (Additive 1)

Glassware was dried overnight at 120° C. in an oven. The glassware wasthen brought into a nitrogen filled dry box. Glycolic acid (1.3786 g,0.01809 mol), lithium tetramethanolatoboron (2.567 g, 0.01809 mol) and15 mL anhydrous acetonitrile (dried overnight with 3 A molecular sieves)were combined with a stir bar. The flask was sealed with a rubber septumand brought out of the dry box. Under flowing nitrogen, a SoxhletExtraction apparatus was added which contained a coarse thimble packedwith 4 A molecular sieves. An oil bath was added and the reaction washeated in stages to 115° C. for 24 hours. The reaction was cooled toroom temperature and under flowing nitrogen the Soxhlet adapter wasremoved. The reactor was connected to a vacuum line equipped with adry-ice trap and the acetonitrile solvent removed under reducedpressure. The crude product was purified under nitrogen by dissolving itunder nitrogen in fresh/dry acetonitrile. 50 mL of −20° C. anhydroustoluene was added and the precipitate collected. This material was driedat under high vacuum to yield 0.460 g of product.

Synthesis of Lithium Difluoro(Glycolato) Borate (Additive 2)

Glassware was dried overnight at 120° C. in an oven. The glassware wasthen brought into a nitrogen filled dry box. Glycolic acid (1.758 g,0.02312 mol), lithium tetrafluoroborate (2.167 g, 0.02312 mol) and 26.5mL anhydrous dimethyl carbonate were combined with a stir bar. The flaskwas sealed with a rubber septum and brought out of the dry box. Underflowing nitrogen, a reflux condenser was added. 1.3 mL (0.01156 mol) ofsilicon tetrachloride was carefully added dropwise by syringe, and thereaction was stirred overnight. Under flowing nitrogen the condenser wasremoved. The reactor then was connected to a vacuum line equipped with adry-ice trap and the solvent removed under reduced pressure. The crudeproduct was purified under nitrogen by dissolving it with refluxingfresh/dry acetonitrile. The material that did not dissolve was filteredand washed with dry acetonitrile. This material was dried at under highvacuum to yield 1.150 g of product.

Representative Cathode Preparation

Representative Preparation of LiMn_(1.5)Ni_(0.45)Fe_(0.05)O₄ CathodeActive Material

The following is a typical procedure used to prepareLiMn_(1.5)Ni_(0.45)Fe_(0.05)O₄ cathode active material. For thepreparation, 401 g manganese (II) acetate tetrahydrate (Aldrich,Milwaukee Wis., Product No. 63537), 125 g nickel (II) acetatetetrahydrate (Aldrich, Product No. 72225) and 10 g iron (II) acetateanhydrous (Alfa Aesar, Ward Hill, Mass., Product No. 31140) were weighedinto bottles on a balance, then dissolved in 5.0 L of deionized water.KOH pellets were dissolved in 10 L of deionized water to produce a 3.0 Msolution inside a 30 L reactor. The solution containing the metalacetates was transferred to an addition funnel and dripped into therapidly stirred reactor to precipitate the mixed hydroxide material.Once all 5.0 L of the metal acetate solution was added to the reactor,stirring was continued for 1 h. Then, stirring was stopped and theprecipitate was allowed to settle overnight. After settling, the liquidwas removed from the reactor and 15 L of fresh deionized water wasadded. The contents of the reactor were stirred, allowed to settleagain, and the liquid was removed. This rinse process was repeated.Then, the precipitate was transferred to two (split evenly) coarse glassfrit filtration funnels covered with Dacron® paper. The solids wererinsed with deionized water until the filtrate pH reached 6.0 (pH ofdeionized rinse water), and a further 20 L of deionized water was addedto each filter cake. Finally, the cakes were dried in a vacuum oven at120° C. overnight. The yield at this point was typically 80-90%.

The hydroxide precipitate was ground and mixed with lithium carbonate.This step was done in 50 g batches using a Pulverisette automated mortarand pestle (FRITSCH, Germany). For each batch the hydroxide precipitatewas weighed, then ground alone for 5 min in the Pulveresette. Then, astoichiometric amount with small excess of lithium carbonate was addedto the system. For 50 g of hydroxide precipitate, 10.5 g of lithiumcarbonate was added. Grinding was continued for a total of 60 min withstops every 10-15 min to scrape the material off the surfaces of themortar and pestle with a sharp metal spatula. If humidity caused thematerial to form clumps, it was sieved through a 40 mesh screen onceduring grinding, then again following grinding.

The ground material was fired in an air box furnace inside shallowrectangular alumina trays. The trays were 158 mm by 69 mm in size, andeach held about 60 g of material. The firing procedure consisted oframping from room temperature to 900° C. in 15 h, holding at 900° C. for12 h, then cooling to room temperature in 15 h.

After firing, the powder was ball-milled to reduce particle size. Then,54 g of powder was mixed with 54 g of isopropyl alcohol and 160 g of 5mm diameter zirconia beads inside a polyethylene jar. The jar was thenrotated on a pair of rollers for 6 h to mill. The slurry was separatedby centrifugation, and the powder was dried at 120° C. to removemoisture.

Preparation of Primer on Aluminum Foil Current Collector—Using aPolyimide/Carbon Composite

To prepare the polyamic acid, a prepolymer was first prepared. 20.6 wt10% of PMDA:ODA prepolymer was prepared using a stoichiometry of 0.98:1PMDA/ODA (pyromellitic dianhydride//ODA (4,4′-diaminodiphenyl ether)prepolymer). This was prepared by dissolving ODA in N-methylpyrrolidone(NMP) over the course of approximately 45 minutes at room temperaturewith gentle agitation. PMDA powder was slowly added (in small aliquots)to the mixture to control any temperature rise in the solution; theaddition of the PMDA was performed over approximately two hours. Theaddition and agitation of the resulting solution under controlledtemperature conditions. The final concentration of the polyamic acid was20.6 wt % and the molar ratio of the anhydride to the amine componentwas approximately 0.98:1. In a separate container, a 6 wt % solution ofpyromellitic anhydride (PMDA) was prepared by combining 1.00 g of PMDA(Aldrich 412287, Allentown, Pa.) and 15.67 g of NMP(N-methylpyrrolidone). 4.0 grams of the PMDA solution was slowly addedto the prepolymer and the viscosity was increased to approximately90,000 poise (as measured by a Brookfield 25 viscometer—#6 spindle).This resulted in a finished prepolymer solution in which the calculatedfinal PMDA:ODA ratio was 1.01:1. 5.196 grams of the finished prepolymerwas then diluted with 15.09 grams of NMP to create a 5 wt % solution. Ina vial, 16.2342 grams of the diluted finished prepolymer solution wasadded to 0.1838 grams of TimCal 30 Super C-65 carbon black. This wasfurther diluted with 9.561 grams of NMP for a final solids content of3.4 wt %, with a 2.72 prepolymer: carbon ratio. A Paasche VL#3 Airbrushsprayer (Paasche Airbrush Company, Chicago, Ill.) was used to spray thismaterial onto the aluminum foil (25 μm thick, 1145-0, Allfoils, BrooklynHeights, Ohio). The foil was weighed prior to spraying to identify thenecessary coating to reach a desired density of 0.06 mg/cm2. The foilwas then smoothed onto a glass plate, and sprayed by hand with theairbrush until coated. The foil was then dried at 125° C. on a hotplate, and measured to ensure that the desired density was reached. Thefoil was found to be coated with 0.06 mg/cm2 of the polyamic acid. Oncethe foil was dried and at the desired coating, the foil was imidized at400° C. following the imidization procedure below:

40° C. to 125° C. (ramp at 4° C./min)

125° C. to 125° C. (soak 30 min)

125° C. to 250° C. (ramp at 4° C./min)

250° C. to 250° C. (soak 30 min)

250° C. to 400° C. (ramp at 5° C./min)

400° C. to 400° C. (soak 20 min)

Preparation of the Paste

The following is a typical procedure used to prepare cathodes. Thebinder was obtained as a 5.5% solution of polyvinylidene fluoride inN-methylpyrrolidone (Solef® 5130 (Solvay, Houston, Tex.)). The followingmaterials were used to make an electrode paste: 4.16 gLiMn_(1.5)Ni_(0.45)Fe_(0.05)O₄ cathode active powder as prepared above;0.52 g carbon black (Denka uncompressed, DENKA Corp., Japan); 4.32 gPVDF (polyvinylidene difluoride) solution; and 7.76 g+1.40 g NMP (SigmaAldrich). The materials were combined in a ratio of 80:10:10, cathodeactive powder:PVDF:carbon black, as described below. The final pastecontained 28.6% solids.

The carbon black, the first portion of NMP, and the PVDF solution werefirst combined in a plastic vial and centrifugally mixed (ARE-310,Thinky USA, Inc., Laguna Hills, Calif.) two times, for 60 s at 2000 rpmeach time. The cathode active powder and the 2nd portion of NMP wereadded and the paste was centrifugally mixed two times (2≦x≦1 min at 2000rpm). The vial was placed in an ice bath and the rotor-stator shaft of ahomogenizer (model PT 10-35 GT, 7.5 mm diameter stator, Kinematicia,Bohemia, N.Y.) was inserted into the vial. The gap between the vial topand the stator was wrapped with aluminum foil to minimize water ingressinto the vial. The resulting paste was homogenized 30 for two times for15 min each at 6500 rpm and then twice more for 15 min at 9500 rpm.Between each of the four homogenization periods, the homogenizer wasmoved to another position in the paste vial.

The paste was cast using doctor blades with a 0.41-0.51 mm gate heightonto aluminum foil (25 μm thick, 1145-0, Allfoils, Brooklyn Heights,Ohio) using an automatic coater (AFA-II, MTI Corp., Richmond, Calif.).The electrodes were dried for 30 min at 95° C. in a mechanicalconvection oven (model FDL-115, Binder Inc., Great River, N.Y.). Theresulting 51-mm wide cathodes were placed between 125 mm thick brasssheets and passed through a calender three times using 100 mm diametersteel rolls at ambient temperature with nip forces increasing in each ofthe passes, starting at 260 kg with the final pass at 770 kg.

Loadings of cathode active material were 7 to 8 mg/cm².

Representative Anode Preparation

The following is a typical procedure used to prepare anodes. An anodepaste was prepared from the following materials: 5.00 g graphite(CPreme® G5, Conoco-Philips, Huston, Tex.); 0.2743 g carbon black (SuperC65, Timcal, Westlake, Ohio); 3.06 g PVDF (13% in NMP. KFL #9130, KurehaAmerica Corp.); 11.00 g 1-methyl-2-pyrrolidinone (NMP); and 0.0097 goxalic acid. The materials were combined in a ratio of 88:0.17:7:4.83,graphite:oxalic acid:PVDF:carbon black, as described below. The finalpaste contained 29.4% solids.

Oxalic acid, carbon black, NMP, and PVDF solution were combined in aplastic vial. The materials were mixed for 60 s at 2000 rpm using aplanetary centrifugal mixer. The mixing was repeated a second time. Thegraphite was then added. The resulting paste was centrifugally mixed twotimes. The vial was mounted in an ice bath and homogenized twice using arotor-stator for 15 min each time at 6500 rpm and then twice more for 15min at 9500 rpm. The point where the stator shaft entered the vial waswrapped with aluminum foil to minimize water vapor ingress to the vial.Between each of the four homogenization periods, the homogenizer wasmoved to another position in the paste vial. The paste was thencentrifugally mixed three times.

The paste was cast using a doctor blade with a 230 μm gate height on tocopper foil (CF-LBX-10, Fukuda, Kyoto, Japan) using the automaticcoater. The electrodes were dried for 30 min at 95° C. in the mechanicalconvection oven. The resulting 51-mm wide anodes were placed between 125μm thick brass sheets and passed through a calender three times using100 mm diameter steel rolls at ambient temperature with nip forcesincreasing in each of the passes, starting at 260 kg with the final passat 770 kg.

Loadings of anode active material were 3 to 4 mg/cm².

Representative Coin Cells Fabrication

Circular anodes 14.3 mm diameter and cathodes 12.7 mm diameter werepunched out from the electrode sheets described above, placed in aheater in the antechamber of a glove box (Vacuum Atmospheres, Hawthorne,Calif., with HE-493 purifier), further dried under vacuum overnight at90° C., and brought into an argon-filled glove box. Nonaqueouselectrolyte lithium-ion CR2032 coin cells were prepared forelectrochemical evaluation. The coin cell parts (case, spacers, wavespring, gasket, and lid) and coin cell crimper were obtained from HohsenCorp (Osaka, Japan). The separator was a Celgard® Monolayer PP BatterySeparator 2500 (Celgard®, Charlotte N.C.). The nonaqueous electrolytesused in the preparation of the coin cells are described in the followingComparative Examples and Examples.

Comparative Examples A Through H and Example 1 and Example 2 Preparationof Electrolyte Compositions

Ethylene carbonate, fluoroethylene carbonate, lithiumhexafluorophosphate (LiPF₆) and NOVOLYTE® battery-grade electrolyte(ethyl methyl carbonate/ethylene carbonate 70/30 vol/vol) are availablefrom BASF, Florham Park, N.J.

To prepare the electrolyte compositions of the Comparative Examples andthe Examples, NOVOLYTE® electrolyte was used, or 2,2-difluoroethylacetate was combined with the appropriate amount of ethylene carbonate,in a nitrogen purged dry box. Molecular sieves (3 A) were added to thesolvent mixture to bring the water content to less than 1 ppm.Sufficient LiPF₆ was added to produce a 1.0 M solution of LiP F₆ in thedried solvent mixture. The additive indicated in Table 1 was then addedto provide the final electrolyte composition.

High Temperature Performance of Coin Cells

The coin cells were cycled twice for formation using a commercialbattery tester (Series 4000, Maccor, Tulsa, Okla.) at ambienttemperature using constant current charging and discharging betweenvoltage limits of 3.4-4.9 V at a current of 12 mA per gram of cathodeactive material, which is approximately a 0.1 C rate. The coin cellswere placed in an oven at 55° C. and cycled using constant currentcharging and discharging between voltage limits of 3.4-4.9 V at acurrent of 240 mA per gram of cathode active material, which isapproximately a 2 C rate.

The results are summarized in Table 1, which provides the solvents andthe weight % of additives used. The column labelled “T80” shows thenumber of discharge/charge cycles needed for the cell to reach 80% ofits initial capacity, and is a measure of cycle life durability. Highervalues in the T80 column indicate longer cycle life durability.

TABLE 1 Example Solvent 70:30 % FEC Additive % Additive T80 Comp. Ex. AEMC/EC 2 None None 99 Comp. Ex. B DFEA/EC 2 None None 116 Comp. Ex. CEMC/EC 0 Additive 1 2 85 Comp. Ex. D DFEA/EC 0 Additive 1 2 58 Comp. Ex.E EMC/EC 0 Additive 2 2 117 Comp. Ex. F DFEA/EC 0 Additive 2 2 52 Comp.Ex. G EMC/EC 2 Additive 1 1 67 Comp. Ex. H EMC/EC 2 Additive 2 1 122 1DFEA/EC 2 Additive 1 1 261 2 DFEA/EC 2 Additive 2 1 354DFEA—difluoroethyl acetate EC—ethylene carbonate FEC—fluoroethylenecarbonate Additive 1—lithium bis(glycolato)borate Additive 2—lithiumdifluoro(glycolato) borate Comp. Ex.—Comparative Example

The results shown in the Table demonstrate that coin cells withelectrolytes containing a non-fluorinated or fluorinated solvent mixtureand FEC alone (Comparative Examples A and B, respectively), or anon-fluorinated or fluorinated solvent mixture without FEC but witheither additive 1 or additive 2 (Comparative Examples C through F), havepoor cycle life (52 to 117 cycles to T80). Coin cells with electrolytescontaining a non-fluorinated solvent mixture, FEC, and either additive 1(Comparative Example G) or additive 2 (Comparative Example H) havesimilar results. However, the combination of the fluorinated solventmixture DFEA/EC with FEC and either additive 1 (Example 1) or additive 2(Example 2) shows that the lifetime is significantly enhanced versusthat of the Comparative Examples.

What is claimed is:
 1. An electrolyte composition comprising: a) anon-fluorinated carbonate; b) a fluorinated solvent; c) at least one ofa lithium glycolatoborate compound represented by Formula I or FormulaII:

d) a fluorinated carbonate; and e) an electrolyte salt.
 2. Theelectrolyte composition of claim 1, wherein the non-fluorinatedcarbonate comprises ethylene carbonate, propylene carbonate, or mixturesthereof.
 3. The electrolyte composition of claim 1, wherein thefluorinated solvent is: a) a fluorinated acyclic carboxylic acid esterrepresented by the formula:R¹—COO—R², b) a fluorinated acyclic carbonate represented by theformula:R³—OCOO—R⁴, c) a fluorinated acyclic ether represented by the formula:R⁵—O—R⁶, or a mixture thereof; wherein i) R¹ is H, an alkyl group, or afluoroalkyl group; ii) R³ and R⁵ is each independently a fluoroalkylgroup and can be either the same as or different from each other; iii)R², R⁴, and R⁶ is each independently an alkyl group or a fluoroalkylgroup and can be either the same as or different from each other; iv)either or both of R¹ and R² comprises fluorine; and v) R¹ and R², R³ andR⁴, and R⁵ and R⁶, each taken as a pair, comprise at least two carbonatoms but not more than seven carbon atoms.
 4. The electrolytecomposition of claim 3, wherein R¹ and R², R³ and R⁴, and R⁵ and R⁶,each taken as a pair, further comprise at least two fluorine atoms, withthe proviso that none of R¹, R², R³, R⁴, R⁵, nor R⁶ contains a —CH₂F or—CHF— group.
 5. The electrolyte composition of claim 3, wherein thefluorinated solvent is a fluorinated acyclic carboxylic acid ester. 6.The electrolyte composition of claim 5, wherein the fluorinated acycliccarboxylic acid ester is CH₃—COO—CH₂CF₂H, CH₃CH₂—COOCH₂CF₂H,F₂CHCH₂—COO—CH₃, F₂CHCH₂—COO—CH₂CH₃, CH₃—COO—CH₂CH₂CF₂H,CH₃CH₂—COO—CH₂CH₂CF₂H, F₂CHCH₂CH₂—COO—CH₂CH₃, CH₃—COOCH₂CF₃,CH₃CH₂—COO—CH₂CF₂H, or mixtures thereof.
 7. The electrolyte compositionof claim 1, wherein the electrolyte composition comprises about 0.5weight percent to about 5 weight percent of a cyclic fluorinatedcarbonate and about 0.01 weight percent to 5 weight percent of at leastone of a lithium glycolatoborate compound of Formula I or Formula II,based on the weight of the electrolyte composition.
 8. The electrolytecomposition of claim 1, wherein the fluorinated carbonate comprisesfluoroethylene carbonate.
 9. The electrolyte composition of claim 1wherein the lithium glycolatoborate borate compound is lithiumbis(glycolato) borate.
 10. The electrolyte composition of claim 1wherein the lithium glycolatoborate borate compound is lithiumdifluoro(glycolato) borate.
 11. An electrochemical cell comprising: (a)a housing; (b) an anode and a cathode disposed in the housing and inionically conductive contact with one another; (c) electrolytecomposition of claim 1 disposed in the housing and providing anionically conductive pathway between the anode and the cathode; and (d)a porous separator between the anode and the cathode.
 12. Theelectrochemical cell of claim 11, wherein said electrochemical cell is alithium ion battery.
 13. The electrochemical cell of claim 12, whereinthe anode comprises an anode active material and the anode activematerial is lithium titanate or graphite.
 14. The electrochemical cellof claim 12, wherein the cathode comprises a cathode active materialexhibiting greater than 30 mAh/g capacity in the potential range greaterthan 4.6 V versus a Li/Li+ reference electrode.
 15. The electrochemicalcell of claim 12, wherein the cathode comprises a cathode activematerial which is charged to a potential greater than or equal to 4.35 Vversus a Li/Li+ reference electrode.
 16. The electrochemical cell ofclaim 12, wherein the cathode active material comprises: a) alithium-containing manganese composite oxide having a spinel structureas active material, the lithium-containing manganese composite oxidecomprising oxides of the formulaLi_(x)Ni_(y)M_(z)Mn_(2−y−z)O_(4−d) wherein x is 0.03 to 1.0; x changesin accordance with release and uptake of lithium ions and electronsduring charge and discharge; y is 0.3 to 0.6; M comprises one or more ofCr, Fe, Co, Li, Al, Ga, Nb, Mo, Ti, Zr, Mg, Zn, V, and Cu; z is 0.01 to0.18, and d is 0 to 0.3; or b) a composite material represented by theformula:x(Li_(2−w)A_(1−v)Q_(w+v)O_(3−e)).(1−x)(Li_(y)Mn_(2−z)M_(z)O_(4−d))wherein: x is about 0 to about 0.1; A comprises one or more of Mn or Ti;Q comprises one or more of Al, Ca, Co, Cr, Cu, Fe, Ga, Mg, Nb, Ni, Ti,V, Zn, Zr or Y; e is 0 to about 0.3; v is 0 to about 0.5. w is 0 toabout 0.6; M comprises one or more of Al, Ca, Co, Cr, Cu, Fe, Ga, Li,Mg, Mn, Nb, Ni, Si, Ti, V, Zn, Zr or Y; d is 0 to about 0.5; y is about0 to about 1; z is about 0.3 to about 1; and wherein theLi_(y)Mn_(2−z)M_(z)O_(4−d) component has a spinel structure and theLi_(2−w)Q_(w+v)A_(1−v)O_(3−e) component has a layered structure; or c) acomposition of the formula Li_(a)Ni_(b)Mn_(c)Co_(d)R_(e)O_(2−f)Z_(f),wherein: R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, Zr, Ti, a rare earthelement, or a combination thereof, and Z is F, S, P, or a combinationthereof; and 0.8≦a≦1.2, 0.1≦b≦0.9, 0.0≦c≦0.7, 0.05≦d≦0.4, 0≦e≦0.2;wherein the sum of b+c+d+e is about 1; and 0≦f≦0.08; or d) a compositionof the formula Li_(a)A_(1−x)R_(x)DO_(4−f)Z_(f), wherein: A is Fe, Mn,Ni, Co, V, or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg,Sr, V, Zr, Ti, a rare earth element, or a combination thereof; D is P,S, Si, or a combination thereof; Z is F, Cl, S, or a combinationthereof; 0.8≦a≦2.2; 0≦x≦0.3; and 0≦f≦0.1; or e) a composition of theformula Li_(a)A_(1−b),R_(b)D₂, wherein: A is Ni, Co, Mn, or acombination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, Zr, Ti, arare earth element, or a combination thereof; D is 0, F, S, P, or acombination thereof; and 0.90≦a≦1.8 and 0≦b≦0.5.
 17. An electronicdevice, transportation device, or telecommunications device, comprisingthe electrochemical cell of claim
 11. 18. A method comprising combining:a) a cyclic non-fluorinated carbonate; b) a fluorinated solvent; c) atleast one of a lithium glycolatoborate compound represented by Formula Ior Formula II:

d) a fluorinated carbonate; and e) an electrolyte salt; to form anelectrolyte composition.